Update troubleshoot-rhc.md

Add Basic SKU limitation

Author: thisisanniefang

articles/load-balancer/troubleshoot-rhc.md

@@ -16,6 +16,8 @@ This article is a guide to investigate issues impacting the availability of your
 
 The Resource Health Check (RHC) for the Load Balancer is used to determine the health of your load balancer. It analyzes the Data Path Availability metric over a **2-minute** interval to determine whether the load balancing endpoints, the frontend IP and frontend ports combinations with load balancing rules, are available.
 
+> Note: RHC is not supported for Basic SKU Load Balancer
+
 The below table describes the RHC logic used to determine the health state of your load balancer.
 
 | Resource health status | Description |